Issue 33390: matmul @ operator precedence (original) (raw)

Created on 2018-04-29 19:49 by FabriceSalvaire, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (5)
msg315918 - (view)	Author: fabrice salvaire (FabriceSalvaire)	Date: 2018-04-29 19:49
I use the new matmul @ operator to implement units, for example 1@u_s for 1 second ( see alpha state implementation at https://github.com/FabriceSalvaire/PySpice/tree/master/PySpice/Unit ). It looks cool, but unfortunately 10@u_s / 2@u_s is actually interpreted as (10@u_s / 2)@u_s instead of (10@u_s) / (2@u_s) due to operator precedence + <<< - <<< * <<< @ <<< / <<< // <<< % https://docs.python.org/3/reference/expressions.html#operator-precedence Since Python is widely used for scientific applications, would it be possible to investigate this topic ?
msg315922 - (view)	Author: Eric V. Smith (eric.smith) *	Date: 2018-04-29 22:54
Operator precedence cannot change without breaking existing code.
msg315923 - (view)	Author: Steven D'Aprano (steven.daprano) *	Date: 2018-04-30 00:10
Precedence issues when dealing with units is unavoidable, I think. The units program on Linux/Unix has similar issues, and they write their own parser and choose their own precedence. https://www.gnu.org/software/units/manual/html_node/Operators.html As Eric says, we can't change the precedence of the @ operator easily, if at all. It would likely require at least one full release (3.8) with a warning, or a future import, and frankly if the numpy community is against it you'll have zero chance of it happening. (On the other hand, if they're in favour of it, you'll have a good chance.) If you still want to pursue this idea further, please take the idea to the numpy and/or Python-Ideas mailing lists for further discussion: https://www.scipy.org/scipylib/mailing-lists.html https://mail.python.org/mailman/listinfo/python-ideas but for now I'm going to set the issue to pending.
msg315933 - (view)	Author: Mark Dickinson (mark.dickinson) *	Date: 2018-04-30 07:42
[Steven] > please take the idea to the numpy and/or Python-Ideas mailing lists for further discussion: But please do read through the previous discussions before starting a new one! See the links in PEP 465, and particularly https://mail.scipy.org/pipermail/numpy-discussion/2014-March/069444.html
msg315934 - (view)	Author: Mark Dickinson (mark.dickinson) *	Date: 2018-04-30 07:43
Gah! Forgot that my post would reset this issue to open. I'm going to close here, since this would be a sufficiently big and unlikely change that it's not going to happen without a python-ideas/python-dev discussion.